Method of treating nickel-containing and vanadium-containing residues

ABSTRACT

Nickel- and vanadium-containing catalysts or petroleum treatment of combustion residues are combined with alkali metal carbonates and/or chlorides and the resulting mixture is melted in the presence of a sulfur carrier with or without carbon which serves to reduce the sulfur to a sulfidic form, a high vanadium, low nickel slag seggregating from a high nickel, low vanadium matte. The matte and slag can be separately tapped and the melt is treated metallurgically to recover nickel while the slag is leached and is thus treated hydrochemically to recover valuable vanadium compounds.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to our commonly assigned copendingapplication Ser. No. 692,022, filed concurrently herewith, based uponGerman application No. P 34 02 357.7 of 25 Jan. 1984.

FIELD OF THE INVENTION

Our present invention relates to a method of recovering nickel andvanadium from nickel-containing and vanadium-containing solid andespecially to a method of treating nickel-containing andvanadium-containing residues of petroleum so as to enable the recoveryof nickel and vanadium therefrom in useful form.

BACKGROUND OF THE INVENTION

Petroleum residues, i.e. solid residues from the processing ofpetroleum, which can be formed during the petroleum-processing operationor upon combustion, and which can contain comparatively large quantitiesof vanadium and nickel at least in part resulting from the presence ofvanadium and nickel in petroleum-processing particles.

It has been proposed to comminute such residues and combine thecomminuted residues with alkali compounds and to roast the resultingmixture in an oxidizing atmosphere in a roasting furnace to obtain asolid composition which could be leached or extracted with water. Thevanadium and nickel could be recovered from the resulting solution.

Generally the residues in question arise from their treatment andutilization of vanadium- and nickel-containing crude oils and petroleumproducts in coking, hydrodemetallization, cracking, gasification andcombustion.

Such residues can contain 10 to 60% by weight V₂ O₅ and 3 to 15% byweight Ni apart from similar but conventionally present amounts of Mg,C, Si, Ca and S. Vanadium- and nickel-containing catalysts are generallyrequired for the production of fats and waxes, for the hardening of fatsby hydrogenation and in heavy oil processing.

The roasting which has been described does not yield products permittingdifferentiated processing to recover nickel compounds on the one handand vanadium compounds on the other. In general, therefore, compounds ofboth vanadium and nickel are recovered together and separation poses aproblem if it is necessary.

Because there have been only limited ways in which these residues couldbe processed economically and to obtain valuable components therefrom,it has generally been less expensive or more cost effective to disposeof the residues in landfills, rather than attempt to recover either thenickel or the vanadium therefrom.

In more general terms, it may be noted that the art has recognized anumber of processes for the processing of nickel-containing andvanadium-containing materials but that these have seldom found their wayinto large scale use in practice. One proposal subjects the material toa reduction of vanadium oxide in an electric furnace for the productionof ferro vanadium. Because of the high content of sulfur, carbon, nickeland silicon in such materials, the ferro vanadium which is produced istreated as second grade and thus has limited utility. It has also beenproposed to subject the entire mass to a reducing operation which isfollowed by separation of vanadium by precipitation or extraction. Weare not aware of commercial utilization of this procedure.

The use of alkali roasting as a means of treating petroleum residues,like proposed acid treatment, has also been found to be of limitedutility and usually has been believed to be desirable only inassociation with nickel-free slags, because a high nickel content of theroasted material detrimentally affects waste water treatment, i.e. thetreatment of waste water formed in the process which cannot bedischarged because of the heavy metal content into the environment.

OBJECTS OF THE INVENTION

Our principal object, with this invention, is to provide a process fortreating nickel-containing and vanadium containing solid residues,especially petroleum residues as the treatable substrate, such thatnickel and vanadium products are obtained directly, i.e. separatetreatment of nickel and vanadium containing intermediates can beavoided.

Another object of this invention is to reduce the possibility ofenvironmental pollution which is brought into systems in which suchresidues are disposed in landfills and the like.

Still another object of our invention is to provide a more efficientmethod of recovering valuable vanadium and nickel in especially usableforms, from such residues.

DESCRIPTION OF THE INVENTION

These objects and others which will become apparent hereinafter areattained, in accordance with our invention, with a method or processwhereby the vanadium- and nickel-containing solid residues, in a dividedor comminuted form, are mixed with superstoichiometric amounts of alkalicarbonates and/or alkali chlorides (generally the alkali metalcarbonates or chlorides and preferably sodium carbonate and/or sodiumchloride), the mixture being brought to a temperature above its meltingpoint and then thereafter the resulting melt material is transformedwith a sulfur carrier in sufficient quantities into a low-vanadiumnickel matte and a low-nickel vanadium slag, the nickel matte and thevanadium slag being then separated mechanically and subjected toseparate treatment in which the nickel and vanadium can be recovered inusable form, i.e. as compounds of desirable metal.

The reference to "superstoichiometric amount" of the alkali metalcarbonates and/or alkali metal chlorides is a reference to a quantity inexcess of that required to stoichiometrically bind the nickel andvanadium in water-soluble form.

The sulfur which participates in the metal-forming reaction can besulfur which is present in the residue or which is added thereto andindeed may be sulfur which may be extracted from petroleum residues ormay be present therein.

If the sulfur present in the residue does not meet the stoichiometricrequirements for metal formation, we can add additional sulfur to themixture before the heating step. In the latter case, the sulfur is addedin its sulfidic form. Naturally, the sulfur can be added after heatingbegins but before the melt is formed or to the melt itself.

We have found it to be advantageous to produce the sulfur required forthe melt formation in situ. In this case, the mixture of the comminutedresidue and the alkali carbonate and/or alkali chloride is combined inaddition with nonsulfidic sulfur carriers and a quantity of carbon sothat when heating occurs subsequently with these materials being addedor by the heat of the melt, the carbon will react with the sulfurcarriers to liberate the sulfur which participates in the melt-formingreaction.

The melting is preferably effected in an electric arc furnace which isused as the melting apparatus. However, other types of furnaces may beused, for example a short drum furnace. The molten vanadium slag and themolten nickel matte are drawn separately from the furnace.

The mechanical preparation of the residue in the form of a comminutedproduct can utilize the fact that the residue may be available in adivided form, e.g. as a fly ash, but generally will require some form ofmechanical subdivision to place it in the optimal state for mixing and,ultimately, for the smelting operation. The best results are obtainedwith a residue in the particle size range from 0.1 mm to about 20 mm andpreferably between 0.5 mm and 20 mm with most effective results beingobtained where the particle size is less than 10 mm.

The smelting of this residue with superstoichiometric amounts of alkalicarbonate and/or chlorides in the presence of sulfur carriers, either inthe form of sulfur carriers intrinsic to the residue or as an additive,appears to enable the immediate formation of a nickel matte from thenickel which may be present in the residue while the vanadium separatesin the form of a slag floating upon the nickel matte.

When the sulfur-containing additive is nonsulfidic sulfur, it isnecessary to supply as well a quantity of carbon at least sufficient tochemically transform the sulfur into its sulfide state. The carbon canbe added in the form of anthracite coal or coke with an appropriateparticle size, i.e. a particle size range as presented above.

It may be found to be advantageous, in accordance with the invention, tosupply at least some carbon even when the residue itself contains sulfurwhich is in nonsulfidic form, if the residue does not contain asufficient amount of reducing components.

Some of the residues which are to be processed in accordance with theinvention will, however, contain large amounts of sulfur andcarbonaceous materials in amounts sufficient to satisfy the reducingrequirements.

Indeed, we may even mix petroleum residues which are rich in sulfur aswell as petroleum residues rich in carbonaceous materials with residuesrich in vanadium and nickel to form the mixture previously described.

When the nickel content of the residues is comparatively low, it may beadvantageous to add to the melt a collector for nickel matte.

The particular melting point of the mixture need not be determined to besatisfactory simply to raise the temperature until melting occurs. Anyconvenient melting apparatus can be used for this purpose if, as we havenoted, the preferred apparatus is either an electric furnace ofconventional design or a short drum furnace.

The separation of the vanadium-containing slag from the nickel matte canbe effected in one of several ways. For example, we can simply tap thenickel matte from beneath the vanadium-containing slag and then treatthe slag with atmospheric oxygen or other oxygen carriers, such assodium nitrate. Alternatively, we can draw off the nickel matte and thevanadium-containing slag together and effect the separation afterhardening or during hardening.

Preferably, however, a third alternative is used wherein the nickelmatte is permitted to remain in the furnace for several charges toaccumulate while the slag is tapped or decanted after each charge. Whenthe residue has little nickel, this allows nickel matte to accumulate inthe furnace until it can be removed, e.g. by permitting it to coolwithin the furnace and removing it as a block.

The vanadium-containing slag can, if necessary, by oxidized further inanother apparatus, e.g. a ladle, the oxidation being effected with airlances or by the addition of chemical substances such as sodium nitrate.The vanadium-containing slag and the nickel matte can both be worked upto recover nickel and vanadium in useful forms, in particular vanadiumcompounds which have been recovered by leaching the slag with water orwater-containing sodium carbonates in the manner described in theaforementioned copending application by any of the methods describedtherein for the treatment of the melt materials. The nickel matte can beworked up by any conventional metallurgical method for the recovery ofnickel or its compounds.

Specific Examples EXAMPLE 1

1 kg of a mixture of carbon and sulfur rich vanadium- andnickel-containing combustion residues of the following composition:

V 16.40%

Ca 1.80%

Mg 7.15%

Ni 5.45%

C 1.84%

S 3.80%

is combined with 300 g sodium carbonate in a comminuted form and isheated to a temperature about 900° C. in a laboratory melting furnace toproduce a low viscosity melt which was then hardened and broken up todetermine the content of the nickel matte and vanadium slag phases. Thefollowing analysis was obtained:

    ______________________________________                                                 Vanadium slag                                                                           Nickel matte                                               ______________________________________                                        V          10.40%      0.015%                                                 Ni         1.53%       53.3%                                                  S          n.b.        18.0%                                                  C          0.2%        n.b.                                                   ______________________________________                                         (n.b. = not significant)                                                 

In the foregoing analysis of the slag and matte, the balance at 100% wasvolatized such as oxygen and nitrogen in the form of compoundschemically bonded or substances which are not relevant to the resultsobtained.

In the vanadium slag the vanadium was present was water-solublecompounds representing 81.6% recovery from the original residue, thenickel recovery in the matte was 61.3%.

EXAMPLE 2

A 30 kg vanadium/nickel petroleum residue having the following analysis:

V 23.4%

Ni 4.1%

S 0.4%

C 1.2%

is mixed with 13.5 g sodium carbonate and 6 kg of Na₂ SO₄ and 1.8 kg ofanthracite coal and melted in a short drum furnace at about 950° C.

To collect the relatively small amount of nickel matte, 300 g ofmetallic lead are added. After cooling and comminuting the slag andnickel matte phase were analyzed with the following results:

    ______________________________________                                                 Vanadium slag                                                                           Nickel matte                                               ______________________________________                                        V          15.18%      0.01%                                                  Ni         1.7%        49.7%                                                  Pb         0.01%       23.8%                                                  S          n.b.        23.5.%                                                 ______________________________________                                    

The water-soluble vanadium amounted to 84.3% recovery and the nickelrecovery was 44.7%.

EXAMPLE 3

30 kg of vanadium- and nickel-containing petroleum residues with thefollowing analysis:

V 28.85%

Ni 11.6%

S 1.5%

C 0.69%

was mixed with 13.5 kg soda, 6 kg Na₂ SO₄ and 1.8 kg anthracite coal.The mixture was melted at about 850° C. in a short drum furnace. Theanalysis of the molten product in terms of the slag and nickel mattegave the following results:

    ______________________________________                                                 Vanadium slag                                                                           Nickel matte                                               ______________________________________                                        V          23.16%      0.01%                                                  Ni         0.31%       73.6%                                                  S          n.b.        21.3.%                                                 ______________________________________                                    

The water-soluble vanadium amounted to 91.2% recovery and the nickelrecovery was about 96.4%.

EXAMPLE 4

10 kg of vanadium- and nickel-containing petroleum residues with thefollowing analysis:

V 28.85%

Ni 11.6%

S 1.5%

C 0.69%

was combined with 4 kg soda, 2 kg Na₂ SO₄ and 0.6 kg anthracite coal,the solids having a particle size of about 0.5 to 2 mm. The mixture wasmelted in an electric furnace at 900° C. and the analysis of thehardened slag and nickel matte gave the following results:

    ______________________________________                                                 Vanadium slag                                                                           Nickel matte                                               ______________________________________                                        V          23.37%      0.01%                                                  Ni         0.43%       66.1%                                                  S          n.b.        25.3.%                                                 ______________________________________                                    

The water-soluble vanadium recovery was 84.3% and the nickel recovery95.0%.

EXAMPLE 5

10 kg of vanadium- and nickel-containing petroleum residues with thefollowing analysis:

V 28.85%

Ni 11.6%

S 1.5%

C 0.69%

was combined with 4. kg soda, 1.0 kg pyrite (FeS₂) and 0.6 kg anthracitecoal. The mixture is smelted at 950° C. in an electric furnace. Theanalysis of the slag and the nickel matte gave the following results:

    ______________________________________                                                 Vanadium slag                                                                           Nickel matte                                               ______________________________________                                        V          24.14%      0.01%                                                  Ni          2.03%      70.3%                                                  S          --          23.2.%                                                 ______________________________________                                    

The water-soluble vanadium yield was 87.3% and the nickel recovery was85.0%.

EXAMPLE 6

5000 kg of vanadium- and nickel-containing petroleum residues with thefollowing analysis:

V 28.85%

Ni 11.6%

S 1.5%

C 0.69%

was mixed with 2250 kg soda, 1000 kg Na₂ SO₄ and 300 kg anthracite coalin a short drum at 950° C. After tapping of the nickel matte which wasprocessed from the slag and the nickel matte which was processedmetallurgically with retention of the slag, further reduction occurredin the slag which was found to be advantageous for the subsequentleaching and chemical recovery of the vanadium compounds by the methoddescribed in the aforementioned application. The slag was subjected tooxidation with air within the furnace for a period of two hours toeliminate the reducing effect of the slag. The following data apply:

    ______________________________________                                        Time           Oxidation Value*                                               ______________________________________                                        Tapping of    3.6                                                             Nickel Matte                                                                  + 1 h         1.6                                                             + 2 h          0.57                                                           ______________________________________                                         *empirically determined measure of the amount of oxidizing agents require     for the reducing power of the slag.                                      

In all of the foregoing Examples, the substitution of sodium chloridefor the sodium carbonate in whole or in part gave similar results,except that the melting temperatures were higher when sodium carbonatewas completely replaced by sodium chloride. In place of the petroleumresidues described, spent V/Ni catalysts could be used.

We claim:
 1. A process for treating a petroleum residue from thecombustion or treatment of petroleum and which contains vanadium andnickel, said process comprising the steps of:mixing said petroleumresidue in a particle size of 0.1 to 20 mm with a superstoichiometricamount of an alkali carbonate and pyrite as a sulfur carrier; smeltingthe mixture in an electric furnace to form nickel matte and a slag;separately tapping said slag and said matte from said furnace wherebysaid slag is virtually free from nickel and said matte is virtually freefrom vanadium; recovering nickel from said matte; and treating said slagwith water to recover the vanadium of said slag in the water in the formof water-soluble vanadium.